- Blood is a specialized type of connective tissue which circulates in the blood vessels.
- A full-term new born has 80 ml/kg blood, a preterm new born has 100 ml/kg blood, an adult male has 70 ml/kg and an adult female has 67 ml/kg blood in their bodies.
- (1) 45% Cellular portion and (2) 55% Liquid portion. Cellular component includes 1) Red blood cells, 2) White blood cells and 3) Platelets.
RBCs are red in color because they containred color pigment called hemoglobin. The normal RBCs count varies with respect to age and sex.In adult females the normal range varies between 4.0 - 5.5 x 106 per microliter and in adult males it ranges from4.5 - 6.0 x 106 per microliter. The normal life span of RBCs is 120 days. The hemoglobin carries oxygen from the lungs to the body cells / tissues / organs etc. and carries back carbon dioxide. After birth the RBCs are usually formed in the bone marrow.
In adult females the normal range variesbetween 4.0 - 5.5 x 106 per microliter and in adult males it ranges from4.5 - 6.0 x 106 per microliter. The normal life span of RBCs is 120 days. Before birth RBCs are formed in the liver and spleen and after birth they are formed in the bone marrow.
White blood cells are white in color. They kill micro organisms and thus try to keep us free from infections, they also plays an important role in our immune system.There are five different types of white blood cells.
- Neutrophils are multi lobed cells having 3 - 5 lobes; it has cytoplasmic granules. Their normal count ranges from 2500 - 5000 per microliter and accounts for 55-75% of the total white blood cells.
The WBCs are usually formed in the bone marrow. The normal life span in our circulation is between 8 – 12 hours.They are the first responders and quickly appear at the site of infection, ingest and destroy the foreign particles. They play an important role in acute inflammation.They are increased in infections like septicemia and may be decreased in typhoid fever.
Lymphocytes are the second most common among the WBCs. They are the smallest among the leukocytes and are approximately the size of a red blood cell. The nucleus stains dark blue to purple, is generally spherical or slightly indented and accounts for most of the cell mass.
There normal count is 2000 – 4000 per microliter and account for 20 – 40 % of the total white blood cells.The normal life span of lymphocytes in our body ranges from few days to months. Lymphocyte mounts the immune response by direct cell attack or antibodies.
Lymphocytes are divided into two types;
a) B Cells type: is formed by the bone marrow, they can form antibodies and helps us in building immunity against viruses, bacteria, etc.
b) T Cells type: is formed by the thymus;they are more than B cells 3:1, they are sub classified as Cytotoxic T cells, T Helper cells and Natural Killer cells. They play an important role in our immune system.
- These are formed by the bone marrow. There normal count is 50 – 300 per microliter which is 1 – 3 % of the total white blood cells.
They remain in our circulation for 8 – 12 hours.The eosinophil's nucleus is bilobed and the cytoplasmic granules are usually orange color. Its function is to kill parasitic worms; destroy antigen-antibody complexes; inactivate some inflammatory chemicals of allergy. Thus they are increased in allergic, parasitic infections, etc.
- It is the largest of the leukocytes and is approximately twice the size of RBC.There normal count varies from 200 - 500 per microliter which is 2-6 %of the total white blood cells. They remain in our circulation for 2 – 3 days. They play an important role in defending host cells infected by pathogenic organism.
The nucleus is kidney shaped and has a gray blue cytoplasm. Its function is phagocytosis i.e. to engulf bacteria, etc.From the blood vessels they enter into the tissues and are then called macrophage. They represent 3% to 8% of the leukocyte population.
- Basophils have lobed nuclei and large blue purple cytoplasmic granules.There normal count is less than 100 per microliter which is lessthan 1% of the total white blood cells.
They remain in our circulation for short time.Their major role is in the production of acute inflammation as result of trauma, infection, etc. Its function is to release histamines and other mediators of inflammation.
- Platelets are small 2-3 microns in size and are like plates. They are formed in the bone marrow from megakaryocytes. Their normal count ranges from 150,000 – 450,000 per microliter.The average lifespan of a platelet is normally just 5 to 9 days
They help in stopping bleeding by accumulating and bridging at the bleeding site.If the number of platelets is too low in the bodythen excessive bleeding can occur.
constitutes 92% water and 8 % solids like fats, proteins, carbohydrates, hormones, enzymes, coagulation factors, vitamins, etc. The plasma acts as suspending medium for the blood cells and carries nourishment to the various cells, tissues and organs of the body. |
